Space and Physics
PUBLISHED
About a decade ago, physicists put forward a theory that proposes how to investigate the quantum nature of time. It can be possible for clocks to experience superposition, where two different states exist at the same time. In this case, the clocks would be ticking at two different rates, one faster and one slower. Researchers now believe that we are close to being able to test this idea.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Superposition is one of the crucial properties of quantum mechanics. Exemplified in the quantum cat experiment, it speaks of something that doesn’t exist in classical physics. In the quantum cat experiment, a fictional cat is locked in a box with a vial of poison, which is activated by a quantum process. The process is in a state of superposition until observed, which is then extended to poison and to the cat, making the cat both alive and dead (no cats were hurt in this).
For a clock to follow the rules of quantum mechanics, it means that it can experience the flow of time at different rates. We know from relativity that depending on your speed or the gravity you are experiencing, time passes differently with respect to an external observer – this is exemplified in the Twin Paradox. Those are two different clocks. Here, they suggest that the same clocks can experience two flows of time in superposition; the quantum cat is both young and old.
“Time plays very different roles in quantum theory and in relativity,” lead author Assistant Professor of theoretical physics Igor Pikovski at Stevens Institute of Technology said in a statement. “What we show is that bringing these two concepts together can reveal hidden quantum signatures of time-flow that can no longer be described by classical physics.”
Over the last few years, optical atomic clocks have broken record after record in precision timekeeping. Atoms are cooled to almost absolute zero, and by using laser pulses, they get a consistent emission of specific frequencies.
These clocks are so sensitive that they can measure gravitational variation due to relativity at a level of meters (and they are being tested on mountains too). They are so sensitive that we will probably have to redefine the second in the coming years. These clocks are sensitive to quantum effects.
“Atomic clocks are now so sensitive, they can detect tiny differences in time caused by just the thermal vibrations at miniscule temperatures,” says Gabriel Sorci, a PhD candidate at Stevens Institute of Technology and co-author of the paper. “But even at the absolute zero temperature, the ground state, the ticking rate will still be affected by just the quantum fluctuations alone.”
The proposed test by the team goes even further. They suggest manipulating the vacuum itself by creating a squeeze state; a clock entangled with such a state will show both relativistic properties and subtle quantum behavior. It should be ticking slower and faster at the same time. They now want to test just that.
“We have the technology to generate the required squeezing and a path to reach the clock precision needed in ion clocks to observe such effects for the first time,” experimentalist and coauthor Christian Sanner at Colorado State University added.
“Physics is still full of mysteries at the most fundamental level. Quantum technologies are now giving us new tools to shed light on them,” Pikovski concluded.
The study is published in the journal Physical Review Letters.
